Conventionally, disposable diapers each including front and rear waist regions and a crotch region extending between these front and rear waist regions wherein the crotch region is provided with an indicator adapted to detect the occurrence of urination are widely known. For example, JP 2007-252659 A (PTL 1) and JP 2004-337386 A (PTL 2) disclose disposable diapers each including top- and backsheets and an absorbent body interposed between these sheets. The backsheet is coated on the inner surface with the hot-melt composition containing the color reaction agent as the indicator. The liquid-permeable sheet is placed between the backsheet and the liquid-absorbent body so that these sheets may prevent the color reaction agent contained in the hot-melt composition from being transferred to the absorbent core.
If the color reaction agent is transferred to the absorbent core, there is a likelihood that the color reaction agent might develop a color reaction due to a slight amount of water vapor absorbed by the absorbent core from the atmosphere but by preventing such transfer of the color reaction agent to the core, the development of the color reaction of the indicators before actual use of the diaper can be prevented.